This article discusses energy-reducing measures attempted and carried out in three oder large office buildings in Chicago. Experience has shown that overcoming the inherently poor standards of airtightness and thermal properties of buildings built post World War II, particularly with curtain walling makes achieving high standards of sustainability a very difficult task. The three buildings in this article are of this vintage, and were first visited by the author in 2001-2003 as part of personal research on the length of service life of equipment in air-conditioned buildings. The buildings were re-visited in 2012 and found that during the intervening period many energy saving measures had been attempted or applied to the buildings, in distinctly different ways, with different levels of intervention.